1. Field of the Invention
The invention relates to a semiconductor chip, chip package and process for forming the same. More particularly, this invention relates to a semiconductor chip, chip package and process for forming the same, wherein wirebonds are suited for being wirebonded to redistribution circuit lines on the semiconductor chip.
2. Description of the Related Art
In recent years, the application of semiconductor in our life has increased with the exuberant electronics industry. As a result, a number of semiconductor manufacturing techniques are also developing rapidly. A typical semiconductor IC manufacturing process can be largely divided into two stages; the first stage is associated with the manufacturing of semiconductor IC chip, which generally comprises the steps of growing singe-crystal silicon, depositing epitaxial layer of Si, manufacturing electronic devices, such as transistors, metal oxide semiconductors (MOS) or passive devices, and manufacturing metal interconnections, . . . etc. The second stage is the packaging process. The purpose of the packaging process is to prevent the IC chips from reaching the outside atmosphere and moisture. What is more, a finished chip package must also be electrically connected to an external circuitry.
In general, a typical electrical connection for a chip package can be processed by a wire-bonding process, a tape automatic bonding (TAB) process, or a flip chip (FC) process. Of these three kinds, the industrial infrastructure for wirebonding is the most mature one, and it has been widely used by various kinds of electronic packages today. In the wire-bonding process, the connection points of a carrier, which can be either a holding substrate or a lead frame, and a chip are joined with a wire electrically connecting the carrier and the chip such that electrical signals can be transmitted/received to/from an external circuitry. Typically, the connection points of the carrier and the corresponding ones on the chip are not placed far apart to make the wire-bonding process simple and to prevent the bonded wires from winding. However, in cases that the layout of the connection points on the carrier is changed or that the chips and carriers are produced by different companies, the wire-bonding process can become less straightforward. Moreover, the electrical properties reduce in that elongated wirebonding wires are used to connect the chip and carrier. As a result, signals transmitted from the chip may be attenuated because of the longer conduction path used to connect the chip and the carrier. Moreover, the strength of the bonding wire becomes a serious issue. For solving the above problem, a redistribution routing can be made to alter the layout of the chip, which leads the chip suitable for being wirebonded thereto. It is worthy of note that the wire-bonding process requires a sufficient loading force to assure the connectivity between the wire and the pad is reliable. Attributed to this process, the elements under the bonding pad will be subjected to an undesired shock during the wire bonding process. Thus, the delicate electronic devices, such as transistors, MOS or passive devices, are typically not to be placed under the wirebond pad to avoid any potential damage caused by such an effect.
R.O.C. patent application Serial No. 90100339, now Patent No. 594,953, teaches the methods and structures of a chip structure with redistribution lines and a process for the same.
FIG. 1 is a cross-sectional view showing a semiconductor chip suited for being wirebonded thereto according to R.O.C. patent application Serial No. 90100339. Referring to FIG. 1, a chip structure 100 is shown with a semiconductor substrate 110, insulation layers 125a, 125b and 125c, metal layers 135a and 135b, a redistribution metal layer 160, a pad 140, a passivation layer 145, an elastomer layer 150, a top polymer layer 190, and a wirebonded wire 200. Multiple IC devices 115 are formed in or on the semiconductor substrate 110, with a trench 120 incorporated in the semiconductor substrate 110 and between the IC devices 115. Furthermore, the insulation layers 125a, 125b, and 125c are formed over the semiconductor substrate 110. The metal layers 135a and 135b and pad 140 are respectively formed on the insulation layers 125a, 125b and 125c. The metal layers 135a and 135b and pad 140 are electrically connected to the IC devices 115 through metal vias 130a 130b, and 130c. 
Referring to FIG. 1, the passivation layer 145 and elastomer layer 150 are formed over the insulation layer 125c. An opening 155 in the passivation layer 145 and elastomer layer 150 exposes the pad 140. The redistribution metal layer 160 extends into the opening 155 and on the elastomer layer 150. The top polymide (PI) layer 190 covers the elastomer layer 150 and the redistribution metal layer 160. An opening 195 is in the top polymer layer 190 and exposes the redistribution metal layer 160. The wirebonded wire 200 is bonded on the redistribution metal layer 160 exposed by the opening 195 in the top polymer layer 190.
The elastomer layer 150 may be polyimide or elastic rubber, which can be prevented from being damaged due to the wirebonding process. However, the above process is costly because the elastomer layer 150 between the redistribution metal layer 160 and the passivation layer 140 should be made.